1. Field of the Invention
This invention relates to an outboard motor steering system.
2. Description of the Related Art
Almost all outboard motor steering systems have up to now been of types operated by human power, such as the tiller handle type used to turn the rudder by manually operating the tiller handle attached to the outboard motor and the remote control type used to remotely operate a steering mechanism through a push-pull cable in response to rotation of a steering wheel manipulated by the operator.
Since human-powered steering systems are disadvantageous because they tend to have an unpleasant steering “feel” owing to, for instance, heavy steering load, as taught in Japanese Laid-Open Patent Application Sho 62 (1987)-125996, an add-on mechanism constituted as a separate unit from the outboard motor and used to power-assist the turning of the tiller handle is known. This mechanism typically includes a steering actuator such as a hydraulic cylinder attached to the front (boat side) of an outboard motor through a link mechanism connected between the actuator and the tiller handle. The add-on steering system using such an actuator also has disadvantages, most notably that its structure is complicated, that it adds to the number and weight of the components, and that it takes up space between the front of the outboard motor and the rear of the boat.
Attempts have been made to overcome these drawbacks. Japanese Laid-Open Patent Application No. Hei 2(1990)-279495 ('495), for example, teaches a steering system including a steering actuator that is not attached to the boat, but is directly attached to the outboard motor, thereby minimizing increase in the number and weight of the constituent components and saving space.
However, the steering system taught by '495 is disadvantageous from the aspect of saving space around the outboard motor because in some operating states of the actuator, the actuator projects from the outboard motor in the horizontal direction. As a result, when two outboard motors are installed side by side in a dual motor configuration, the installation space must be enlarged by the amount of projection of the actuator so as to prevent interference between the outboard motors. This problem is more serious when the actuator is enlarged so as to increase the steering force (torque), since this requires the actuator to project farther in the horizontal direction.